Bis((1-oxo-2,6,7-trioxa-1-phospha bicyclo(2.2.2)oct-4-yl)methyl)2,5 dibromoterephthalate

ABSTRACT

1. BIS((1 - OXO - 2,6,7 - TRIOXA - 1 - PHOSPHABICYCLO (2,2,2)-OCT-4-YL)METHYL) 2,5-DIBROMOTEREPHTHALATE.

3,849,522 BIS((1-0X0-2,6,7-TRIOXA 1 PHOSPHA BICYCLO[2.2.2]OCT-4-YL)METHYL) 2,5 DIBROMOTEREPH- THALATE William A. Hills,Trenton, N.J., assignor to FMC Corporation, New York, NY. No Drawing.Filed June 11, 1973, Ser. No. 368,732 Int. Cl. C07d 105/04; C08f 45/58US. Cl. 260-927 R 1 Claim ABSTRACT OF THE DISCLOSURE A novel compound,bis((1-oxo-2,6,7-trioxa-l-phosphabicyclo [2.2.2] oct-4-yl methyl)2,S-dibromoterephthalate,

which is a highly effective flame-retardant additive for polyesters, andflame-retardant polyester compositions containing it.

This invention relates to flame-retardant polyester compositions. Moreparticularly, the invention relates to flameretardant polyester fibers,films and molded articles wherein the flame-retardant additive is anovel phosphate-containing ester of 2,5-dibromoterephthalic acid.

Polyester compositions containing organic phosphorus and organic halogencompounds are known and are dis closed, for example, in US. Pat. Nos.3,356,631, issued Dec. 5, 1971, to Jackson et al.; 3,645,962, issuedFeb. 29, 1972, to Schwarz; 3,681,281, issued Aug. 1, 1972, to Juelke etal.; 3,688,001, issued Aug. '29, 1972, to Exner et al.; 3,708,328,issued Jan. 2, 1973, to Kelkheim et al.; and West German Patent No.2,001,125 (1970) to Caldwell et al. (Eastman Kodak Company). Theaforesaid patents deal with methods and additives for imparting flameretardance to polyesters.

However, it has always been desirable to provide more efficient flameretardants which are thermally stable and which can be incorporated intomolten polyester prior to formation of fibers, films or molded articles.

According to the present invention, there has been discovered a novelcompound, bis((1-oxo-2,6,7-trioxa-1-phosphabicyclo[2.2.2]oct-4-yl)methyl) 2,5-dibromoterephthalate, which isa highly eifective flame retardant for polyesters and is particularlysuited for use in connection with polyester fibers.

The novel compound of the present invention is rep resented by thefollowing formula:

and may be prepared by reacting 4'-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane and 2,5-dibromoterephthaloylchloride in acetonitrile solvent utilizing pyridine as a catalyst.

A further embodiment of the present invention resides in polyesterfibers, films and molded articles containing from about to 25% byweight, based on the combined weight of polyester and flame retardant,of the novel compound of the present invention.

The polyesters which are rendered flame-retardant in accordance with thepresent invention includes both the fiberand film-forming linearsaturated polyesters derived from saturated aliphatic and aromaticdicarboxylic acids and saturated diols and linear unsaturated polyesterswhich are principally employed for casting and molding applications.

The fiberand film-forming saturated polyesters are prepared fromdicarboxylic acids such as terephthalic acid, isophthalic acid, adipicacid, diphenyl-4,4-dicarboxylic acid (bibenzoic acid),4,4'-di(carboxyphenyl)methane, 2,

United States Patent 0 "ice 6-naphthalene-dicarboxylic acid,1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexane-dicarboxylic acid andthe like. Diols generally employed to prepare the fiberand film-formingpolyesters are the saturated aliphatic, saturated cycloaliphatic oraromatic diols, preferably the lower alkane diols such as ethyleneglycol, propylene glycol and butylene glycol. Other exemplary diolsinclude ethylene diglycol, dimethylolcyclohexane, 1,6-hexanediol,pxylylenediol and the like. Particularly preferred are fiberandfilm-forming polyesters prepared from ethylene glycol and terephthalicacid. These fiberand film-forming polyesters generally have an averagemolecular weight of at least about 10,000.

Unsaturated polyesters are characterized in that they are based onmacromolecules with a polyester backbone in which both a saturated acid,e.g., phthalic, isophthalic or adipic acid, and an unsaturated acid suchas maleic or fumaric acid are condensed with a diol. A three dimensionalstructure is obtained by cross-linking the linear polyester backbonethrough the unsaturated acid component with a vinyl monomer, which isusually styrene. Conventional peroxide initiators are employed, such asbenzoyl peroxide or cumene hydroperoxide. The crosslinking monomers alsomay act as solvents for the polyester so as to produce a liquid, lowviscosity polyestermonomer system which is useful for casting andmolding applications. Before addition of the vinyl monomer, thepolyester backbone usually has a molecular weight of about 1,000 to5,000.

A particularly preferred embodiment of the present invention resides inproviding flame-retardant spun polyester fibers such as polyethyleneterephthalate, poly(1,4- cyclohexylenedimethylene)terephthalate orpolyethylene 2,6-naphthalenedicarboxylate spun fibers havingsignificantly improved flame-retardant characteristics.

As is known in the art, polyester fibers are conventionally prepared bythe so-called melt spinning technique. In this method, the moltenpolyester is extruded under pressure through a spinneret plate having aplurality of small circular openings about 0.009 inch in diameter. Thespinning is carried out at a temperature of from about 260 to 300 C. forpolyethylene terephthalate fibers. The polymeric polyester has beenpreviously prepared either by the batch method or by the continuouspolymerization technique.

Thus, in view of the conditions employed in the melt spinning process,there are a significant number of problems to be overcome insuccessfully incorporating an effective flame retardant during meltspinning. The flame retardant must be thermally stable, it must be bothunreactive with and soluble in the molten polyester. In addition, theflame retardant must have a low volatility at spinning temperatures andshould not in any way interfere with the operation of the spinneret. Theflame re tardant should also have no substantial adverse elfect upon thephysical properties of the spun fiber.

The novel flame-retardant compound of the present invention, bis( (1 oxo2,6,7 trioxa l-phosphabicyclo- [2.2.2]oct-4-yl)methyl)2,5-dibromoterephthalate meets all these important criteria and isparticularly suitable for use in connection with the melt spinningprocess for producing polyester fibers.

Generally speaking, from about 5 to 25 of the novel flame-retardantcompound of the present invention is employed based on the combinedweight of polyester and additive, i.e., 5 to 25 parts by weight of flameretardant and to parts by weight of polyester. Preferably about 10 to22% by weight of the novel flame-retardant additive is employed.

Flame-retardant polyester fibers prepared in accordance with the presentinvention may be used as such or may be blended with other fibrousmaterials such as cotton, rayon,

nylon, acetate, acrylics and the like, and such blends are well known tothose in the textile art.

Polyesters useful for molding compositions will generally containinorganic reinforcing fillers such as mineral silicates, silica gel,asbestos, clay, talc, and the like which improve the physical propertiesof the molding compounds, with glass fibers being a preferredreinforcing additive for such compositions at concentrations of about 10to 50% by weight of the total molding composition.

Of course, flame-retardant polyester fibers, films and molded articlesprepared in accordance with the present invention may contain a widevariety of additional ingredients such as plasticizers, dyes, heat andcolor stabilizers, pigments, antioxidants, antistatic agents and variousother special purpose additives employed in the processing of polyestercompositions.

The invention is further illustrated by the following examples which arenot to be considered as limitative of its scope. All parts andpercentages are by weight of (based on) the total weight of thecomposition and temperatures are in degrees centigrade, unless otherwisestated.

Example I A mixture of 72 g. (0.4 mole) of 4-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane and 72 g. (0.2 mole)2,5-dibromoterephthaloyl chloride and 400 ml. of acetonitrile containing7 drops of pyridine was placed in a one liter flask equipped with amagnetic stirrer, reflux condenser and drying tube, and was heated undera gentle reflux until the evolution of hydrochloride gas stopped. Asolid precipitated from the reaction mixture as the reaction proceeded.The mixture was filtered and 127 g. of white solid was collected. Thesolid was washed several times with 10% sodium carbonate solution, thenwith distilled water and dried to give 103.3 g. of white solididentified as bis((1-oxo-2,6,7-trioxal-phosphabicyclo[2.2.2]oct 4yl)methyl) 2,5 dibromoterephthalate having a melting point 310 C.

Example 11 The flame retardancies of polyethylene terephthalate (PET)plaques containing the compound prepared in Example I were determined bymeasuring the Limiting Oxygen Index (LOI) of the plaques.

The plaques were first prepared as follows:

One brass plate (6" x 6" chrome plated) is placed on the bottom (chromeside up), a 6" x 6" x spacer 6, stainless steel) is placed on a 6 /2." x6 /2" sheet of aluminum foil and the edges are folded over and pressedinto place. This is then placed on the brass plate. A 6 gram 10-meshscreened sample of ground polymer (containing the flame-retardantadditive) is spread evenly on the foil in the 5 /2" x 5 /2" squareframed by the spacer. A fiberglass fabric (5%" x 5 /2) is placed overthe polymer. A second 6 gram portion of the polymer-additive compositionis spread evenly over the fiberglass fabric. A6 x 6" sheet of aluminumfoil is placed over the polymer and a second chrome plated brass plateis put on top (chrome side in). The mold assembly is placed in ahydraulic press previously heated to 275 C., the plates are closedgently and to allow melting (about 3 minutes) then the pressure isincreased rapidly to 10,00012,000 pounds. After one minute the pressureis released and the mold quenched in a cold water bath. The foil isremoved and the composite cut out. The 5 /2" square plastic composite ofPET resin and glass fabric is cut into 3 /2 x /z strips which are driedat 100 C. for one hour.

The LOI test is made by supporting the 3%" x /z sample strip in aU-shaped frame which is mounted in a cylindrical open chamber.Controlled mixtures of oxygen and nitrogen gases are admitted into thebase of the chamber and allowed to displace the normal atmosphere. Whenan equilibrium atmosphere in the chamber is obtained, the sample isignited with a butane gas flame by contacting the flame to the top edgeof the sample. If it fails to ignite, the oxygen ratio of the atmosphereis increased to a level where the flame will just propagate. Conversely,if the sample strip ignites and the flame propagates, the oxygen ratioof the atmosphere is reduced to a level where flame propagation isvirtually zero. The LOI is the minimum percentage concentration of theoxygen atmosphere in which the test sample will ignite and permit flamepropagation.

The -LOI test was introduced in 1966 (Fennimore et al., Modern Plastics,43, 141 (1966)) and is the basis for ASTM-D-2863-70. The apparatus usedas the Oxygen Index Flammability Tester (Model JD14) manufactured by MKMMachine Tool Co., Inc.

The LOI results for PET plaques containing various amounts of the noveladditive prepared in Example I are set forth in the table below:

TABLE I.-FLAMMABILITY DATA Percent additive Sample of Example I L01 1.None 21. 0 2. 10. 5 29. 2 3 21. 0 37. 2

Example III Twenty parts of the novel compound of Example I wasmix-melted with parts of polyethylene terephthalate under N and theadmixture was observed using a hot stage microscope. The sample meltedwithout decomposition at 249-252 C. and became fluid; decomposition didnot take place. The temperature was raised to 285 C. and held there for10 minutes, and then to 290 C. and maintained at 290 C. for anadditional 10 minutes. No visible increase in viscosity was observed norwas there observed any darkening or other evidence of decomposition.This example demonstrates the thermal stability of the blend.

What is claimed is:

1. Bis((1 oxo 2,6,7 trioxa 1 phosphabicyclo [2.2.2]-oct-4-yl)methyl)2,S-dibromoterephthalate.

References Cited UNITED STATES PATENTS 3,310,609 3/1967 Baranauckas eta1. 260927 R ANTON H. SU'ITO, Primary Examiner US. Cl. X.R. 260 45.7 P

1. BIS((1 - OXO - 2,6,7 - TRIOXA - 1 - PHOSPHABICYCLO(2,2,2)-OCT-4-YL)METHYL) 2,5-DIBROMOTEREPHTHALATE.